In Parliament Mr Mann described the Dickens dossier as “intriguing to say the least”.

He said that a former deputy director of MI6, George Kennedy Young, was involved in a right-wing Conservative group which gathered details on alleged paedophiles within the Commons.

Young, also known as ‘GK’ who died in 1990, was not named as a paedophile but Mr Mann described him as a “manipulator” who had been involved in “dubious” political activities, including a campaign to set up a private army.

“We need to know why the file disappeared,” Mr Mann said in a Westminster Hall debate.

The modern-day MI6 headquarters, Thames House Photo: Alamy

He later told TheTelegraph: “Young is the key figure in the file.

“He is the person behind what was going on. We need to know more about him.”

A specific location identified in the dossier – which Mr Mann refused to name – would be a crucial lead for police, he added.

Last year’s review into missing documents by Peter Wanless, the head of the NSPCC, and Richard Whittam QC said it had “found nothing to support a concern that files had been deliberately or systematically removed or destroyed to cover up organised child abuse”.

“It’s imperative the Government reopens the review to see why this file was not given to them,” said Mr Mann, the Labour member for Bassetlaw.

Mr Mann has now handed a copy of the dossier to the police.

Karen Bradley, a junior Home Office minister, said: “I understand the police are reviewing the documents and I look forward to hearing the outcome of that work.”